By default, the sparklet has no data to show. You need to extend the Sparklet
instance and a fetch method which receives one argument which is a callback
function.

var mysparklet = Sparklet.extend({

fetch:functionfetch(next){

asyncoperation(function(err, data){

next(err, data);

});

}

})

The data that you pass in the next function should be an array of objects.
These objects should have a date and value key. By default we assume that
you provide the date in a YYYY-MM-DD format. If your using a different format
either change it using a .map operation on your array or change the format
property on the pagelet: